/*
 * Copyright (c) from 2000 to 2009
 * 
 * Network and System Laboratory 
 * Department of Computer Science 
 * College of Computer Science
 * National Chiao Tung University, Taiwan
 * All Rights Reserved.
 * 
 * This source code file is part of the NCTUns 6.0 network simulator.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation is hereby granted (excluding for commercial or
 * for-profit use), provided that both the copyright notice and this
 * permission notice appear in all copies of the software, derivative
 * works, or modified versions, and any portions thereof, and that
 * both notices appear in supporting documentation, and that credit
 * is given to National Chiao Tung University, Taiwan in all publications 
 * reporting on direct or indirect use of this code or its derivatives.
 *
 * National Chiao Tung University, Taiwan makes no representations 
 * about the suitability of this software for any purpose. It is provided 
 * "AS IS" without express or implied warranty.
 *
 * A Web site containing the latest NCTUns 6.0 network simulator software 
 * and its documentations is set up at http://NSL.csie.nctu.edu.tw/nctuns.html.
 *
 * Project Chief-Technology-Officer
 * 
 * Prof. Shie-Yuan Wang <shieyuan@csie.nctu.edu.tw>
 * National Chiao Tung University, Taiwan
 *
 * 09/01/2009
 */

#include <stdio.h>
#include <string.h>

#include "library.h"

// $FreeBSD: src/lib/libz/crc32.c,v 1.5.2.1 2003/02/01 13:33:12 sobomax Exp $

unsigned int crc_table[256] = {
	0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
	0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
	0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
	0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
	0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
	0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
	0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
	0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
	0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
	0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
	0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
	0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
	0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
	0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
	0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
	0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
	0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
	0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
	0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
	0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
	0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
	0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
	0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
	0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
	0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
	0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
	0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
	0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
	0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
	0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
	0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
	0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
	0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
	0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
	0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
	0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
	0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
	0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
	0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
	0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
	0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
	0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
	0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
	0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
	0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
	0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
	0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
	0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
	0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
	0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
	0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
	0x2d02ef8dL
};

/* ========================================================================= */
#define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
#define DO2(buf)  DO1(buf); DO1(buf);
#define DO4(buf)  DO2(buf); DO2(buf);
#define DO8(buf)  DO4(buf); DO4(buf);

/* ========================================================================= */
unsigned int crc32(unsigned int crc, char *buf, int len)
{
	if (buf == NULL)
		return 0L;
	crc = crc ^ 0xffffffffL;
	while (len >= 8) {
		DO8(buf);
		len -= 8;
	}
	if (len)
		do {
			DO1(buf);
		} while (--len);
	return crc ^ 0xffffffffL;
}

/*
//  A simple version of Header Checksum Sequence using XOR
u_int8_t hcs(char *buf, int len)
{
	u_int8_t x = 0;
	while(len) x^=buf[--len];
	return x;
}
*/

u_int8_t hcs(char *buf, int len)
{
	// Generator: D^8 + D^2 + D + 1

	char crc = 0x00;
	int i;
	char b;

	for (i = 0; i < len; i++) {
		crc ^= buf[i];

		for (b = 0; b < 8; ++b) {
			if (crc & 0x80)
				crc = (crc << 1) ^ 0x07;
			else
				crc = (crc << 1);
		}
	}
	return crc;
}

// Checksum function Source Code modify from the website below:
//                            http://www.netfor2.com/contents.htm
/*
**************************************************************************
Function: ip_sum_calc
Description: Calculate the 16 bit IP sum.
***************************************************************************
*/

//u_int16_t ip_sum_calc(u_int16_t len_ip_header, u_int16_t buff[])
u_int16_t ip_sum_calc(u_int16_t len_ip_header, char buff[])
{
	u_int16_t word16;
	u_int32_t sum = 0;
	u_int16_t i;

	// make 16 bit words out of every two adjacent 8 bit words in the packet
	// and add them up
	for (i = 0; i < len_ip_header; i = i + 2) {
		word16 = ((buff[i] << 8) & 0xFF00) + (buff[i + 1] & 0xFF);
		sum = sum + (u_int32_t) word16;
	}

	// take only 16 bits out of the 32 bit sum and add up the carries
	while (sum >> 16)
		sum = (sum & 0xFFFF) + (sum >> 16);

	// one's complement the result
	sum = ~sum;

	return ((u_int16_t) sum);
}

/*
**************************************************************************
Function: udp_sum_calc()
Description: Calculate UDP checksum
***************************************************************************
*/

u_int16_t udp_sum_calc(u_int16_t len_udp, u_int16_t src_addr[],
		       u_int16_t dest_addr[], bool padding,
		       u_int16_t buff[])
{
	u_int16_t prot_udp = 17;
	u_int16_t padd = 0;
	u_int16_t word16;
	u_int32_t sum;
	int i;

	// Find out if the length of data is even or odd number. If odd,
	// add a padding byte = 0 at the end of packet
	if ((padding & 1) == 1) {
		padd = 1;
		buff[len_udp] = 0;
	}
	//initialize sum to zero
	sum = 0;

	// make 16 bit words out of every two adjacent 8 bit words and
	// calculate the sum of all 16 vit words
	for (i = 0; i < len_udp + padd; i = i + 2) {
		word16 = ((buff[i] << 8) & 0xFF00) + (buff[i + 1] & 0xFF);
		sum = sum + (unsigned long) word16;
	}
	// add the UDP pseudo header which contains the IP source and destinationn addresses
	for (i = 0; i < 4; i = i + 2) {
		word16 =
		    ((src_addr[i] << 8) & 0xFF00) +
		    (src_addr[i + 1] & 0xFF);
		sum = sum + word16;
	}
	for (i = 0; i < 4; i = i + 2) {
		word16 =
		    ((dest_addr[i] << 8) & 0xFF00) +
		    (dest_addr[i + 1] & 0xFF);
		sum = sum + word16;
	}
	// the protocol number and the length of the UDP packet
	sum = sum + prot_udp + len_udp;

	// keep only the last 16 bits of the 32 bit calculated sum and add the carries
	while (sum >> 16)
		sum = (sum & 0xFFFF) + (sum >> 16);

	// Take the one's complement of sum
	sum = ~sum;

	return ((u_int16_t) sum);
}


#if 0
int main(int argc, char **argv)
{
	char buf[1024];
	char buf2[1024] =
	    { 0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00,
		0x04, 0x70, 0x6F, 0x70, 0x64, 0x02, 0x69, 0x78, 0x06, 0x6E,
		0x65, 0x74,
		0x63, 0x6F, 0x6D, 0x03, 0x63, 0x6F, 0x6D, 0x00, 0x00, 0x01,
		0x00, 0x01
	};
	int len, result = 0, i;
	while (fgets(buf, sizeof(buf), stdin)) {
		len = strlen(buf2);
		printf("Len = %d\n", len);
		result = crc32(result, buf, len);

	}
	printf("CRC32 = %08x\n", result);
}
#endif
